The present invention relates to a method and system for providing advice to an operator of a vehicle that the vehicle is being operated under conditions which may lead to vehicle rollover or, alternatively, to loss of control of the vehicle due to the manner in which the brakes of the vehicle have been applied. Desirably, the information is provided to the vehicle operator following the occurrence of vehicle operating conditions presenting an unacceptably increased risk so that the driver may be educated that these driving conditions have occurred and to avoid such conditions in the future.
Due to the differences in the center of gravity height and mass (load) of vehicles, the rollover threshold of commercial vehicles can vary significantly from load to load and vehicle to vehicle. Commercial vehicles typically include trucks as well tractors which are towing one or more semi-trailers. In the case of trucks, a load cargo area is carried by the truck itself. In the case of tractors with semi-trailers, a load cargo area is typically found in the trailers. In the case of truck tractors, a load cargo area is typically found both on the truck and in a towed trailer. Because trucks are constantly picking up and dropping off loads, the center of gravity of the vehicle and any trailers being towed thereby often varies from time to time. It is the vehicle operator""s responsibility to be aware that these variations exist and to adjust the vehicle""s speed appropriately, particularly when cornering or braking, so as to operate the vehicle safely. For purposes of explanation, the rollover threshold can be viewed. as operating conditions under which a vehicle would be expected to roll from a position which the vehicle wheels are traveling in contact with the ground toward a position where the vehicle is on its side or otherwise rolls over. In addition to vehicle load, a number of factors affect the rollover threshold, such as vehicle speed, braking conditions, the sharpness of any turn being undertaken, the slope of the road (e.g., crown and banking of curves), the stiffness of the vehicle and trailer suspension, as well as other factors.
The University of Michigan Transportation Research Institute has previously worked on a roll stability advisor system. This research work employed an instrumented fifth-wheel to estimate the trailer""s center of gravity height and a lateral accelerometer to determine the lateral acceleration of the vehicle. Estimate of the center of gravity height and lateral accelerometer measurements were used as inputs to dynamically assess the percent of rollover threshold at which the vehicle was being operated. The rollover status information was displayed continuously to the driver. Instrumenting a fifth-wheel tractor-trailer coupling device on a commercial vehicle is not practical, due to reliability and durability problems, and is relatively expensive.
Road User Research of Australia has previously developed and field-tested a road stability advisor system for tractor-tanker-trailer vehicles. The Road User Research system employed Apriori rollover threshold knowledge about these vehicles, along with a lateral accelerometer located at the center of gravity of the tank-trailer, to dynamically assess the rollover threshold. The Apriori rollover threshold knowledge employed in the Road User Research system was not understood to be updated as the load on the vehicle changed. That is, the Road User Research system is understood to assume the rollover threshold is the same whether the vehicle was loaded or empty. Indicator lights on the dash of the vehicle were illuminated to provide the vehicle operator with information about the percent of rollover threshold approached during vehicle operation when predetermined rollover thresholds were exceeded.
Although these and other rollover detection systems have previously been known, a need nevertheless exists for an improved system for evaluating rollover risks and advising vehicle operators of such risks. In addition, an improved system for advising vehicle operators of braking conditions which can lead to loss of control of the vehicle is also desirable.
The present invention is described throughout with reference to several embodiments. The invention is not limited to the specifically described embodiments. In addition, the invention encompasses features and method acts and steps which are novel and unobvious, both individually and in various combinations as set forth in the claims below.
In accordance with one aspect of an embodiment, the mass of the vehicle and any towed trailers is determined. For example, for a tractor-trailer combination in which two semi-trailers are being towed, the loaded vehicle and trailers may be weighed to determine the mass. As another alternative option, the load at the drive axles of the vehicle may be measured and supplemented by the measured load or by an assumption of the measured load to be carried by the other axles. Other mechanisms for actually measuring the mass of the vehicle may be used. Although relatively straightforward, measuring methods are not very practical or cost effective. This is particularly true in the case of tractor-trailer combination vehicles where any one of numerous trailers may be transported by the same tractor with the trailers having various configurations. Also, the mass is affected by numerous other factors such as how and the extent to which the vehicle and trailers have been loaded. Therefore, it is desirable to dynamically estimate the mass of the vehicle to account for these variables. In one specific approach, the vehicle mass may be estimated based on a summation of longitudinal forces acting on the vehicle and deriving the mass from an application of Newton""s Second Law under such conditions. In particular, the mass of the vehicle and towed trailers, if any, may be repetitively estimated at least at selected times when the vehicle is being driven to provide a dynamically varying estimate of the mass.
As another aspect of this particular embodiment, a rollover acceleration value is determined. The rollover acceleration value may comprise a critical rollover threshold estimate related to the lateral acceleration of the vehicle at which the vehicle has an unacceptably increased risk of rolling over. More specifically, the critical rollover threshold may be a value which approaches or is equal to the threshold at which the vehicle and towed trailers, if any, would be expected to roll over under the conditions at which the vehicle is being operated. In a specific approach described below, the rollover acceleration value is determined based on the mass or estimate of the mass of the vehicle and load. The rollover acceleration value may be assigned based upon a rule set. This rule set may be embodied in a lookup table which lists rollover acceleration values for a particular type or types of vehicle having a mass which corresponds to the estimated mass. Consequently, when the mass is determined or estimated, the table can be checked to find a rollover acceleration value for that particular mass. As the mass varies, the table may again be checked to determine the applicable rollover acceleration value for the new estimate of mass of the vehicle. Alternatively, the rule set may be embodied in one or more formulas and may be specifically tailored to given vehicles with given types of loads. Desirably, the rollover values may be assigned based upon an assumed manner in which the cargo area being transported by the vehicle is loaded.
As a further aspect of an embodiment, the lateral acceleration of the vehicle under driving conditions may be measured or otherwise determined. For example, an acceleration sensor may be used which is mounted to the circuit board of an automatically modulated braking system (ABS system) which is used to control the braking of at least selected wheels of the vehicle. Although desirable, it is not required that a sensor be located at this location and other mechanisms for determining the lateral acceleration of the vehicle may be used. Lateral acceleration measurements from a sensor may be processed to remove fixed and variable offsets introduced into the measurements by factors such as any tilting (off-horizontal) mounting of the sensor, arising from electronics, and/or due to variable factors such as the crown on the road on which the vehicle is being driven. The variable factors may be compensated for dynamically, depending upon the conditions under which the vehicle is being operated.
The resulting lateral acceleration determination in accordance with an embodiment is compared with the rollover acceleration value. The closer or nearer the lateral acceleration value approaches the rollover acceleration value, the riskier the driving conditions. That is, the risk of vehicle roll over is increased as the rollover acceleration value is approached. In comparing the rollover value to the lateral acceleration value, a ratio of these two values may be obtained. A rollover risk score may be determined from this ratio. For example, the rollover risk score may be the percentage of the rollover acceleration value achieved by the lateral acceleration value. One or more rollover acceleration value thresholds may be established. These thresholds may be set at predetermined or variable levels below the critical rollover acceleration value or estimate. Alternatively, if the rollover acceleration value is conservative (e.g., established at a level below which the vehicle would roll over), then the thresholds may be equal to or in excess of the rollover acceleration value. In the event the risk of rollover, as determined from the comparison, exceeds one or more of these thresholds, the rollover risk is indicated to the vehicle operator based on the comparison. As a result, the vehicle operator is alerted to the fact that the vehicle has been operated under increased rollover risk conditions. In many cases, vehicle operators, particularly inexperienced operators, do not recognize that these conditions have taken place. By alerting the vehicle operator of the existence of such conditions, the vehicle operator is provided with feedback so that, in the future, the operator will have learned to avoid these conditions.
Rather than distracting the driver with rollover warnings at the time the rollover conditions have taken place, the driver may be alerted to such conditions following the event. In other words, once the rollover risk thresholds are no longer being exceeded, the messages may be sent to the driver to indicate the extent (e.g., the highest threshold that was reached) to which a rollover risk was present during the just completed vehicle operation maneuver. By providing contemporaneous after the fact feedback to the driver, behavior modification (e.g., safer driving) is encouraged. The system provides an effective driver training tool as feedback to the driver is typically provided while the vehicle is still being driven by the driver.
In addition to indicating to the driver that a rollover risk has occurred, and desirably the level of risk, a recommendation may also be indicated to the driver of corrective action that could have been taken to reduce the risk. For example, a speed reduction recommendation may be provided to the vehicle operator. The recommended speed reduction may be varied depending upon the rollover risk level that was determined to exist. The rollover risk levels and corrective action recommendations may be communicated to the driver in any suitable manner, such as with visual or auditory signals or both. Indicator lights may be used, for example, with the lights that are illuminated providing information to the driver as to the level of risk that was determined, and also to indicate the corrective action recommendation, if such recommendations are being made. These messages may desirably be communicated to the driver using an alphanumeric message and display.
The corrective action recommendation may, for example, include a specific speed reduction recommendation. The reduction in speed that is recommended may vary with varied vehicle operating conditions. In addition, a first proposed reduction in vehicle speed recommendation may be made in the event the rollover risk fell into one of at least two categories and a second, different, recommended reduction in speed recommendation may be made to the driver if the rollover risk fell into a different risk category. The speed reduction recommendation is typically a higher recommended reduction in speed for higher risk categories.
In one specific embodiment, three categories of rollover risk are established ranging from highest to lowest risk. Operating conditions in the lowest risk category in this specific example result in no speed reduction recommendation. In contrast, a first speed reduction is recommended in the event the rollover risk falls into the second category and a greater speed reduction recommendation is made in the event the rollover risk falls within the highest category. In indicating the rollover risk to the vehicle operator, the risk levels may be distinguished visually as well as auditorally. For example, if the rollover risk is in the lowest category, the message may be steadily presented to the driver or flashed at a first low rate. In addition, an auditory signal may be provided to the vehicle operator, for example a short alert beep. In the event the rollover risk falls into the second category, the message may be flashed at a rate which is greater than the flashing rate for the low category. In addition, the auditory signal may be of a longer duration and/or be repetitive. In addition, if the highest risk category was determined, the message may be flashed at yet a higher rate. In addition, the auditory signal may be longer or otherwise more intense. One way of accomplishing flashing of a signal is to alternately present a message indicating the level of risk and a speed reduction recommendation with the rate of shifting from screen to screen being increased with higher risk.
To increase the training aspects of the system, the messages may continue until they have been acknowledged by the vehicle operator. For example, a keypad or other data entry device may be provided. The operator may be required to enter data (e.g., push a button or key) in order to terminate the message. In this manner, the driver is required to acknowledge that the driver has been made aware of the risky driving conditions. An icon on the message as well as on the button or data entry key may coincide visually to indicate to the driver which button is to be pressed to acknowledge the feedback.
As yet another aspect of an embodiment, the vehicle may have an automatically modulated braking system which in a conventional manner controls the braking of at least selected wheels of the vehicle. The control of braking at a wheel is modulated under certain wheel slip conditions as determined by the automatically modulated braking system (ABS system). Such systems, for example those which are commercially available from MERITOR-WABCO, typically produce wheel modulation or first signals indicating the modulation of the wheels. From these first signals a determination can be made whether one or more of the wheels are being modulated or having their braking function controlled by the ABS system. ABS braking systems also typically produce wheel speed signals. These wheel speed or second signals indicate the rate at which acceleration of the vehicle (including deceleration of the vehicle) is taking place. In accordance with this embodiment, the first signals may be evaluated to determine whether one or more wheels are being modulated by the automatically modulated braking system. If such modulation is taking place, this indicates a wheel modulation hard-braking event. In addition, the second signals may be evaluated to determine whether deceleration of the vehicle is occurring at too high of a rate. For example, the deceleration may be evaluated to determine whether it is in excess of a first or rapid deceleration rate. To avoid spurious signals, a requirement may be imposed that the rapid deceleration rate is exceeded for a first predetermined time period, which may be varied in duration. In the event deceleration at a rate which exceeds the first deceleration rate for the specified time period is determined, this condition may be considered to be a rapid deceleration hard-braking event. The braking conditions under which a rapid deceleration hard-braking event is indicated may be varied.
In one specific embodiment, a first level of hard-braking event may be indicated in the event a wheel modulation hard-braking event is detected without the detection of a rapid deceleration hard-braking event. In addition, a second level of hard-braking event may be indicated in the event a rapid deceleration hard-braking event is determined without the occurrence of a wheel modulation hard-braking event. Moreover, a third level of hard-braking event may be indicated in the event both the modulation wheel hard-braking event and rapid deceleration hard-braking events have occurred. The existence of hard-braking events indicates the possible operation of a vehicle during braking conditions may lead to a higher risk of lost vehicle control.
Desirably, the determination of the occurrence of first, second and third hard-braking event levels is accomplished after braking conditions have concluded which led to the determination of the particular hard-braking event level. For example, a hard-braking event may be deemed to have commenced when any of the hard-braking levels have been achieved and ended when all of the hard-braking event levels are no longer present. The highest level (first, second and third with third being the highest level) achieved during the hard-braking event may be indicated to the vehicle operator. This indication may be made shortly after the event conditions have ended to provide contemporaneous feedback to the driver. Although hard-braking events may be indicated to the driver at a time they are taking place, this is less desirable. That is, by delaying the indication of the hard-braking events, the driver is not distracted with warning or other messages at the time hard-braking is occurring. As in the case of rollover advisories, advice as to the levels of hard-braking events may be indicated in various ways, such as by alphanumeric messages. Auditory and visual messages, which may be varied depending upon the level of hard-braking event that was detected, may also be used. Furthermore, the vehicle operator may be required to acknowledge the receipt of the hard-braking event messages before a display or other indication of the messages is ended.
Under certain operating conditions, hard-braking events indicate proper operation of a vehicle. Desirably, a vehicle operator should not be warned of a hard-braking event under conditions where hard-braking events were appropriate. In accordance with one specific embodiment, the indication of hard-braking events may be blocked for braking events in which the lateral acceleration value exceeds a predetermined threshold. For example, the indication of a hard-braking event may be blocked if the lowest rollover threshold is detected in the event the hard-braking event detector is being used with a rollover advisor. In other words, at higher levels of lateral acceleration, typically hard-braking events are appropriate. Alternatively, the hard-braking events may be displayed in all cases.
The various risk of rollover levels and hard-braking event levels may be assigned priorities and displayed accordingly. In addition, the levels of risk and of hard-braking events may be varied to more closely approach actual driving conditions. That is, vehicle operators may tend to ignore warning messages and the like if they do not correspond to actually occurring high rollover risk and unacceptable hard-braking event conditions.
The driver or vehicle dispatcher may want to know the number of hard-braking events and rollover risks that have taken place during a particular vehicle trip or which have taken place during a particular leg or segment of a vehicle trip. These rollover advisory events and hard-braking events, when they occur, may be stored in memory such as a vehicle log. This information may be recalled at appropriate or desirable times. In addition, the information may be sent via satellite or otherwise to a remote dispatcher or a remote location.
Regardless of how the rollover risk is determined, an aspect of one embodiment involves determining a reduction in the speed recommendation and communicating the vehicle speed reduction recommendation to the vehicle operator. The speed reduction recommendation may be varied with the evaluated risk of vehicle rollover. For example, a vehicle speed reduction recommendation of a first magnitude may be made in the event of a first rollover risk evaluation. In addition, the magnitude of the vehicle speed reduction recommendation may be of a second, higher amount, in the event the rollover risk is at a second, higher level. Also, as a further aspect of this embodiment, the recommendations for speed reduction are desirably made following the conclusion of driving conditions which led to the vehicle rollover risk. These recommended speed reductions may be made in miles per hour or kilometers per hour. The magnitude of the speed reduction for a given rollover risk may be varied. An alphanumeric display may be used for communicating the recommended reductions in speed and rollover risk levels to the vehicle operator.
The above aspects of embodiments may be implemented in a vehicle operator advising system or apparatus and as methods. Again, the embodiments are particularly useful in advising vehicle operators of vehicle driving conditions which create unacceptably high vehicle rollover risks and/or unacceptably high hard-braking events. Again, the present invention is not limited to embodiments with all of the above features and method acts, but is directed toward such features and acts which are novel and unobvious, both individually as well as to combinations and sub-combinations thereof.